Dyeing of leather



United States Patent Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed May 31, 1957, Ser. No. 662,587

Claims. (Cl. 8-43) This invention relates to a new process for dyeing leather, and more particularly to a process for dyeing leather on one side only with azoic (ice color) dyestuffs.

It has long been the desire in the trade to be able to dye leather in such a manner that the color is fast to washing, crocking, and light. The conventional acids, direct and basic colors frequently lack the necessary fastness properties and often tend to bleed considerably when treated in a soap liquor. Such bleeding is of course detrimental to the color properties of the dyestuifs in addition to introducing problems in connection with staining all adjacent areas or garments.

Azo dyestufiis have been applied to leather by the immersion or brushing method and mostly from neutral or acid baths, the constitution of the dyestuif determining whether the depth of the dyeing on the leather is shallow or deep. In spraying methods, spirit soluble azo dyestuffs have been used. These methods are often very troublesome and do not always adequately fulfill all requirements with respect to fastness and the like.

Attempts have been made to dye leather by impregnation with an azoic dye coupling component followed by coupling with a diazo component. However, due to the high alkalinity of the coupling component treating liquor, thecoupllng component exhausted poorly, the conditions for efiicent coupling with the diazo component were improper, and the shades obtained were dull, weak, and of poor wash-, crockand light-fastness. Moreover, the quality of the leather was adversely affected, desirable properties therein being destroyed. The presence of free, unreacted coupler in leather drum dyed with naphthols further increases the tendency towards crocking. In addition, the tendency of the leather to shrink in the highly alkaline naphthol coupling bath was generally inhibited or prevented by addition to the bath of formaldehyde, whereby highly desirable yellows and other shades produced with acylacetarylide couplers could not be obtained in view of the deleterious effect thereon of the formaldehyde.

It has also been proposed to dye leather with azo dye- 'stufis by applying the coupling component to the leather 'the desired fastness properties.

The dyeing of certain types of leather on only one side is highly desirable. This is particularly true of glove leathers in addtion to shoe, garment and upholstery leathers, where bleeding and/or rubbing off of a 'color from the opposite surface would be often objectionable.

It is an object of this invention to provide a novel process for dyeing leather with azoic dyestuffs. Another 2,967,751 Patented Jan. 10, 1961 object of this invention is the dyeing of leather on only one side with azo.c dyestuffs. Still another object of this invention is the provision of a process wherein leather may be dyed on only one side by the azoic dyeing method. Other objects and advantages will appear as the description proceeds.

The attainment of the above objects is made possible by the instant invent.on which comprises a process for dyeing leather on one side comprising spraying such leather with an aqueous alkaline solution containing, in about equivalent amounts, an ice color coupling component devoid of solubilizing groups and an ice color diazo compound devoid of solubilizing groups and solubilized and stabilized against azoic coupling on the alkaline side by reaction with an organic amine containing at least one solubilizing group and at least one replaceable hydrogen atom attached to an amino nitrogen atom, and then developing the ice color on the leather by treatment with an acidic material. It has been found that the above defined process of this invention enables the attarnment of dyeings having improved properties with respect to levelness, wash fastness, light fastness and/0r crock fastness, and the like. The problems of loW substantivity of the coupling component in the leather, and/or uneven exhaustion thereof on the leather from a dyebath are thereby eliminated since the bath containing the coupling component is maintained separately from the leather and only a sufiicient amount thereof is sprayed on the leather to achieve the desired depth of shade. Better control of the dyeing process and better dyeings are obtained. The process enables the dyeing of only one side of the leather in an easily controlled and expeditious manner. Contamination and/ or careful control of dyebaths to maintain proper dye component concentrations therein during dyeing is eliminated. Further, loss of footage due to shrinkage is minimized, the need for a formaldehyde addition to the coupling solution is eliminated, and acylacetarylide type couplers may be employed.

All types of leather may be dyed in accordance with the. process of this invention, whether tanned with vegetable, syntan, or metal (chrome, alum, Zinc, zirconium, etc.) tanning agents in any desired manner.

The ice color diazo components employed in the instant invention are well known in the art and are in general derived from dazotizable primary amine compounds devoid of solubilizing groups such as carboxylic or sulfonic acid groups. Included among such compounds are such aromatic and heterocyclic amines as anilines, xenylamines, naphthylamines, benzidines, aminocarbazoles, aminofuranes, aminothiazoles, aminoarylsulfones,aminodiphenyl ethers, aminobenzophenones, aminofiuorenones, aminoazo compounds, and the like. As specific examples of such compounds, theremay be mentioned aminoazo toluene, 4-chloro-2-nitroaniline, S-chloro-o-toluidine, 4 nitro o toluidine, 2,5-dichloroaniline, 4-benzamido- 2,5-diethoxyanilin e, 4-amino-m-anisidine, 4-nitro-o-anisidine,4-chloro-o-anisidine, l-aminonaphthalene, l-aminoanthraquinone, dianisidine, S-chloro-4-nitro-o-anisidine, aminobenzophenone, aminodiphenylsulfone, 2,6-dichloro-l,4-phenylenediamine, benzrdine, 4,4-diaminostilbene, and the like.

Prior to incorporation in the bath employed in the instant invention, the diazotizableprimary amine compound is diazotized in known manner as by treatment with sodium nitrite and dilute hydrochloric acid, and the resulting ice color diazo compound solubilized and stabilized against azoic coupling on the alkaline side in known manner by reaction with an organic amine containing at least one solubilizing group and at least one, replaceable hydrogen atom attached to an amino nitrogen atom. The resulting stabilized ice color diazo compounds are often referred to as diazoamino, diazoimino, and diazoamidine compounds and the like, and generically under the term diazoamino compounds. Such stabilized ice color diazo compounds are available as such on the market, as for example under the trademark Levamine (General Aniline & Film Corporation). The organic amines employed for such stabilization are well known and are reacted with the ice color diazo compound in proportions sufficient to react with all the diazo groups therein. As representative of such stabilizing organic amines, there may be mentioned by way of example, N- methyl taurine, sarcosine, 4-sulfo-2-aminobenzoic acid, S-sulfo-Z-methylaminobenzoic acid, 5-sulfo-2-ethylaminobenzoic acid, proline, pyrrolidine-alpha-sulfonic acid, glucamine, methyl glucamine, guanyl urea-N-sulfonic acid, guanyl taurine, N-nitroguanyl urea, Z-biguanidyl naphthalene-l-sulfonic acid, creatine, cyanamide, and the like. Carboxylic and sulfonic acid groups are preferred as the solubilizing groups, but other groups are known such as ammonium salt groups and polyalcohol radicals and the like.

In general, the stabilized ice color diazo compounds employed in the instant invention are formed by the reaction of the diazo derivative of a strongly basic diazotizable primary amine with a stabilizing amine of weak basicity. Such stabilized compounds do not undergo a coupling reaction in alkaline media in the presence of an ice color coupling component, but in the presence of acidic reagents, they split, permitting coupling of the ice color diazo compound with the ice color coupling component.

The ice color coupling components operative in the instant invention, also Well known in the art, are devoid of solubilizing groups such as carboxylic or sulfonic acid groups. In general, these coupling components may be characterized as compounds having an active methylene group, an enolizable keto group or an aromatic hydroxy group inducing coupling, usually in orthoor para-position, preferably the former, to said hydroxy group. Such compounds are typified by the acylacetarylides (e.g. anilides, etc.), the pyrazolones, and aromatic hydroxy compounds capable of coupling. As acylacetarylides there may be mentioned acetoacetic acid arylides, furoyl acetic acid arylides, terephthaloyl-bis-acetic acid arylides, and the like. As pyrazolones, there may be mentioned 1- phenyl-3-methyl-S-pyrazolone, l-p-tolyl-3-methyl-5-pyrazclone, 3 methyl 5 pyrazolone, 5 pyrazolone, 1,3-dimethyl 5 pyrazolone, l-(p-chlorophenyl)-3-methyl-5- pyrazolone, 1-(p-nitrophenyl)-3-methyl-5-pyrazolone, 1- (o-methoxyphenyl)-3-methyl-5-pyrazolone, l-(m-aminophenyl)-3-methyl-5-pyrazolone. l-methyl-S-pyrazolone, 1- phenyl-S-pyrazolone, 1-phenyl-5-pyrazolone-3-carboxylic acid methyl ester, l-phenyl-5-pyrazolone-3-carboxylic acid ethyl ester, and other -5-pyrazolones either unsubstituted or substituted in the 1- and/or 3-positions by non-solubilizing radicals. The aromatic (carbocyclic or heterocyclic) hydroxy compounds useful as coupling components herein generally include phenols, resorcinols, 1- and Z-napthols, benzonaphthols, hydroxy-benzofiuorenones, hydroxyazo compounds such as (o-hydroxyaniline resorcinol), coppered, and aniline 8-amino-2- naphthol and the like, in addition to arylides of betahydroxy aromatic and heterocyclic carboxylic acids. Illustratively, examples of such arylides (e.g. anilides, etc.) which may be employed in the process of the instant invention are 3-hydroxy-2-naphthoic acid arylides, 3-hydroxy-Z-anthroic acid arylides, 3-hydroxy-2-carbazole carboxylic acid arylides, 3-hydroxy-2-furane carboxylic acid arylides, 2 hydroxy 11H-benzo-(a)carbazole-3- carboxylic acid arylides, hydroxydibenzothiophene carboxylic acid arylides and the like. These and other such ice color coupling components operative herein are disclosed in Diserens, Chemical Technology of Dyeing and Ifrinting, volume 1, pages 213 to 224 (Reinhold Publishing Corp., 1948), Lubs, Chemistry of Synthetic Dyes and Pigments, pages 182 through 192 (Reinhold Pub lishing Corp., 1955), and Adams, Journal of the So-' ciety of Dyers and Colorists, volume 67 (1951), beginning at page 223. Those azoic coupling components containing an aromatically bound free amino group enable the attainment of further improved results. Typical amino substituted couplers include aminonaphthols, such as 1-amino-7-naphthol; aminophenols, such as m-diethylaminophenol, aminoresorcinol, rn-aminophenol; aminoazophenols and naphthols, such as 6-hydroxy-4-(o-nitrophenylazo) 1 naphthyl-amine; aminophenylprazolones, such as methyl mand p-aminophenyl-pyrazolone; acylacetarylides substituted in the aryl radical by an amino group, such as acetoacet-m-toluylene-diamine; ohydroxycarboxylic acid arylides having an amine substit uent in the aryl radical, such as 3-amino-3-hydroxy-2- naphthanilide.

The baths employed in the process of the instant invention should contain in known manner approximately equivalent proportions of the stabilized ice color diazo component and ice color coupling component whereby substantially no unreacted components remain after coupling has taken place on the leather. Thus, a tetrazotized diazo component will require double the usual amount of coupler. Suitable compositions containing the stabilized ice color diazo component (diazoamino compound) and ice color coupling component are available on the market, for example under the trademark Rapidogen (General Aniline & Film Corporation). They are for the most part available in powder form, and in many cases in stabilized concentrated solution form. The dyebaths employed in the process of the instant invention should have a pH of more than 7, preferably about 9 to 13, and may contain a combined dye component (diazoamino compound and ice color coupling component) concentration ranging from about 0.5 to 30% by weight, use of concentrations of about 2-10% being usual. Both the dye component concentration and the total amount of dyebath applied to the leather will in general depend upon the desired fluidity of the dyebath to facilitate application, the depth of shade desired, the absorbency and other surface characteristics of the leather and the like.

As a further feature of this invention, it has been found that in those cases where a relatively high coupling pH (e.g. 6-7) is necessary, as with dianisidine tetrazo, and/or where the leather is highly acidic, even stronger, more brilliant and more uniform dyeings may be obtained when a water-soluble or readily water-dispersible saturated lower non-aromatic amine is added to the dyebath. As examples of such amines, there may be mentioned mono-, diand triethanolamine, monoand dimethyland ethylamines, ethylethanolamine, diethyl ethanolamine, isopropanolamine, 2-methyl-2-aminopropanol, butylamine, amylamine, ethylenediamine, trimethylenediamine, diethylenetriamine, diethylethylenediamine, morpholine, and the like. If the non-aromatic amine is gaseous, the equivalent amount is employed in the form of its solution. In general, concentrations of about 0.5 to 15% of the amine by weight in the dyebath are sulficient to achieve the desired results. Improved results are particularly noticeable in the production of black dyeings. While the mechanism by which the improved results are attained is not fully understood, it is believed that it may be due to a bufiering action, facilitating the maintenance on the leather of an optimum pH range during the coupling reaction. In some cases, a substance such as sodium acetate or sodium citrate or the like may be employed to achieve a similar buffering action.

The dyebaths employed in the instant invention may be prepared in any desired manner and the components mixed in any desired order. It may be desirable in some instances to employ an auxiliary organic solvent in solution concentration of about 5 to 50% by weight to assist in solubilizing the components of the solution, such solanol, ethanol, propanol, butanol, cyclohexanol, and mixtures thereof and the like. If desired, known assistants, thickening agents, dispersing agents and the like may be included.

To provide improved solubility of the components in the dyebath and to aid in increasing surface penetration of the leather and level dyeing results, addition of a surface active agent to the dyebath is advisable, those of the water-soluble anionic surface active type being preferred. Such agents are well known in the art and are in general organic sulfates and sulfonates containing :at least carbon atoms. Included in this group are the alkyl arylsulfonates such as dodecylbenzene sulfonate, isopropylnaphthalene sulfonate, diisobutylnaphthalene sulfonate, and the like, N-higher acyl taurines such as N- oleoyl-N-methyl taurine, N-tallow acyl-N-methyl taurine, N-tall oil acyl-N-ethyl taurine, N-palmitoyl-N-methyl taurine, and the like, higher aliphatic sulfates and sulfonates such as lauryl sulfate, Oxo tridecylsulfate, sulfonated and sulfated castor oil, higher fatty acid esters of isethionic acid and the like and sulfonated polycarboxylic acid esters such as diamyl sulfosuccinate, dioctylsulfosuccinate, and the like. All of these sulfates'and sulfonates are preferably employed in the form of their alkali metal salts with sodium or potassium, although other salts may be employed such as those with amines such as methylamine, ethanolamine, morpholine, and the like. Such agents are generally employed in amounts of about 0.2 to 2% by weight in the dyebath.

In carrying out the process of the instant invention, a dyebath of the type above described, diluted with water to the concentration required for the attainment of proper spray consistency and the desired depth of shade, is sprayed on the leather in the usual manner, for example with an ordinary spray gun or any other spray device suitable for applying liquids in finely divided form. The leather may be sprayed with up to 3 or more passes, depending upon the results desired. One gallon of spray dyebath for each 200 to 500 sq. ft. of leather is usually sufiicient. It will be understood that brushing is to be considered as equivalent to spraying in carrying out the process of the instant invention.

Following application of the dyebath to the leather as above described, the dyed leather is, if desired after drying, treated with an acidic material to liberate the free diazonium salt and permit-coupling thereof with the ice color coupling component on the leather. Suitable acidic materials for this purpose are well known in the art, including acetic acid, formic acid, tartaric acid, glycollic acid, citric acid, salts such as acid sodium sulfate, monosodium phosphate and the like. Although treatment of the dyed leather with this acidic material in the form of a vapor is possible, better results are generally obtained by applying the acidic material in the form of an aqueous solution of suitable concentration, which may generally range from about 1 to 10% of the acidic material by Weight in the solution. The dyed leather may be passed through the acidic solution, but it is preferred to apply the acidic solution to the dyed leather by spraying whereby certain manipulative and operational advantages pointed out above are attained. Following development of the color on the leather, the leather may be washed, dried and otherwise treated in known manner.

It will be understood that in carrying out the process of the instant invention, ornamental and decorative affects may be obtained by local application of the dyebath to the leather. Although more or less acceptable results are sometimes obtained by sequential application of the diazoamino compound and ice color coupling component, in either order, to the leather instead of from the same dyebath as described above, such application involves added expense in equipment, time and labor, increased difiiculty in controlling the dye component solution concentrations and amounts, etc., loss of intimate, molecular contact between the dye component molecules tending towards incomplete coupling, dullness of shade, loss of fastness and the like.

The following examples, in which parts are by weight unless otherwise indicated are illustrative of the instant invention and are not to be regarded as limitative:

Example 1 A 5 g. Rapidogen mixture comprising an equivalent amount of a diazoamino compound (Levamine) from dianisidine, tetrazotized and stabilized with N-methyl taurine, and, as coupler, 8-amino-5-(benzeneazo)-2-naphthol, is dissolved with 3 cc. NaOH 40 B., and 15 cc. warm water. This solution is diluted with cc. water, and the resulting Rapidogen dyebath is sprayed, using three passes, onto about 15 sq. ft. of chrome tanned syntan (phenol sulfonic acid-formaldehyde condensation product) stained grain glove leather. The leather is then sprayed with about 300 cc. of a 7% aqueous formic acid solution. A deep jet black color develops on the sprayed side of the leather.

Example 2 The procedure of Example 1 is repeated, but employing as diazoamino compound S-nitro-o-anisidine, tetrazotized and stabilized with N-ethyl-sulfo-anthranilic acid and as coupler a 1:1 mixture of 3-hydroxy-2-naphthoic acid m-nitroanilide and 3-hydroxy-2-naphthoic acid 0- anisidine. A bright red coloration develops on the sprayed side of the leather.

' Example 3 The procedure of Example 1 is repeated, but employing as diazoamino compound 4-benzoylamino-Z-methoxy- '5-methylaniline, diazotized and stabilized with N-methyl taurine, and as coupler 3-hydroxy-2-naphthoic acid anilide. A deep violet shade develops on the sprayed side of the leather.

Example 4 The procedure of Example 1 is repeated but employing as diazoamino compound 4-benzoylamino-2,S-diethoxyaniline, diazotized and stabilized with N-methyl taurine, and as coupler 3-hydroxy-2-naphthoic acid anilide. A bright greenish-blue coloration develops on the sprayed side of the leather.

Example 5 The procedure of Example 1 is repeated but employing as diazoamino compound S-nitro-o-anisidine, tetrazotized and stabilized with N-ethyl-sulfoanthranilic acid, and as coupler bis-acetoacet-o-tolidide. A satisfactory yellow coloration develops on the sprayed side of the leather.

Example 6 The procedure of Example 1 is repeated, but applied to vegetable tanned cowhide instead of the chrome tanned syntan stained glove leather. A deep black coloration develops on the sprayed side of the leather.

Example 7 When in Example 1, there is added to the dyebath 5 g. of (a) monoethanolamine, (b) diethanolamine, (c) triethanolamine or (d) ethylenediamine, somewhat deeper shades are obtained.

In the above examples, the addition to the dyebath of cc. of ammonium hydroxide 26 B. also improves the colors obtained.

This invention has been disclosed with respect to certain preferred embodiments, and there will become obvione to persons skilled in the art various modifications, equivalents or variations thereof which are intended to be included within the spirit and scope of this invention.

I claim:

1. A process for dyeing leather on one side comprising spraying such leather with an aqueous alkaline bath consisting essentially of an aqueous alkaline solution of in about equivalent amounts, an ice color coupling component devoid of solubilizing groups and an ice color diazoamino component which is an ice color diazo compound devoid of solubilizing groups, which compound has been solubilized and stabilized against azoic coupling on the alkaline side by reaction with an organic amine containing at least one solubilizing group and at least one replaceable hydrogen atom attached to an amino nitrogen atom, and then developing the ice color on the leather by treatment with an acidic material.

2. A process as defined in claim 1 wherein said coupling component is of the acylacetarylide type.

3. A process as defined in claim 1 wherein said coupling component is of the pyrazolone type.

4. A process as defined in claim 1 wherein said coupling component is an aromatic hydroxy compound capable of coupling.

5. A process as defined in claim 4 wherein said aromatic hydroxy compound is a beta-hydroxy aromatic carboxylic acid arylide.

6. A process for dyeing leather on one side comprising spraying such leather with an aqueous alkaline bath consisting essentially of an aqueous alkaline solution of a saturated lower non-aromatic amine and, in about 8 equivalent amounts, an ice color coupling component devoid of solubilizing groups and an ice color diazoamino component which is an ice color diazo compound devoid of solubilizing groups, which compound has been solubilized and stabilized against azoic coupling on the alkaline side by reaction with an organic amine containing at least one solubilizing group and at least one replaceable hydrogen atom attached to an amino nitrogen atom, and then developing the ice color on the leather by treatment with an acidic material.

7. A process as defined in claim 6 wherein said coupling component is of the acylacetarylide type.

8. A process as defined in claim 6 wherein said coupling component is of the pyrazolone type.

9. A process as defined in claim 6 wherein said coupling component is an aromatic hydroxy compound capable of coupling.

10. A process as defined in claim 9 wherein said aromatic hydroxy compound is a beta-hydroxy aromatic carboxylic acid arylide.

References Cited in the file of this patent UNITED STATES PATENTS 2,405,165 Pepper Aug. 6, 1946 2,815,259 Glietenberg et al. Dec. 3, 1957 FOREIGN PATENTS 707,884 Great Britain Apr. 28, 1954 OTHER REFERENCES Diserens: Chem. Tech. of Dyeing and Printing, vol. 1, 1948, Reinhold Pub. C01fp., N.Y., p 297.

Venkataraman: The Chem of Synthetic Dyes, vol. 1, 1952, Academic Press Inc., pub. N.Y., pp. 227, 228 and 689-691. 

1. A PROCESS FOR DYEING LEATHER ON ONE SIDE COMPRISING SPRAYING SUCH LEATHER WITH AN AQUEOUS ALKALINE BATH CONSISTING ESSENTIALLY OF AN AQUEOUS ALKALINE SOLUTION OF IN ABOUT EQUIVALENT AMOUNTS, AN ICE COLOR COUPLING COMPONENT DEVOID OF SOLUBILIZING GROUPS AND AN ICE COLOR DIAZOAMINO COMPONENT WHICH IS AN ICE COLOR DIAZO COMPOUND DEVOID OF SOLUBILIZING GROUPS, WHICH COMPOUND HAS BEEN SOLUBILIZED AND STABLIZED AGAINST AZOIC COUPLING ON THE ALKALINE SIDE BY REACTION WITH AN ORGANIC AMINE CONTAINING AT LEAST ONE SOLUBILIZING GROUP AND AT LEAST ONE REPLACEABLE HYDROGEN ATOM ATTACHED TO AN AMINO NITROGEN ATOM, AND THEN DEVELOPING THE ICE COLOR ON THE LEATHER BY TREATMENT WITH AN ACIDIC MATERIAL. 